Is LCT useful for blood sugar?

The question of whether the LCT gene (lactase persistence) is useful for blood sugar requires nuanced interpretation. Lactase breaks lactose into glucose and galactose, so dairy consumption in lactase-persistent individuals can cause a modest blood sugar rise. However, lactose has a relatively low glycemic index, and its impact on fasting glucose or long-term glycemic control is small. In lactose intolerance (lactase non-persistence), undigested lactose reaches the colon and is fermented by bacteria, producing gas but not glucose; this does not lower blood sugar. Evidence for a direct benefit of LCT testing for blood sugar management is weak. Consumer DNA tests typically report LCT variants (e.g., rs4988235) for lactose intolerance, not for blood sugar. Clinical utility is limited; a balanced diet with moderate dairy intake is more relevant. Safety note: If lactose intolerance is suspected, consult a physician before eliminating dairy.